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1da177e4 LT |
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2 | bttv and sound mini howto | |
3 | ========================= | |
4 | ||
25985edc | 5 | There are a lot of different bt848/849/878/879 based boards available. |
1da177e4 LT |
6 | Making video work often is not a big deal, because this is handled |
7 | completely by the bt8xx chip, which is common on all boards. But | |
8 | sound is handled in slightly different ways on each board. | |
9 | ||
10 | To handle the grabber boards correctly, there is a array tvcards[] in | |
11 | bttv-cards.c, which holds the informations required for each board. | |
12 | Sound will work only, if the correct entry is used (for video it often | |
13 | makes no difference). The bttv driver prints a line to the kernel | |
14 | log, telling which card type is used. Like this one: | |
15 | ||
16 | bttv0: model: BT848(Hauppauge old) [autodetected] | |
17 | ||
18 | You should verify this is correct. If it isn't, you have to pass the | |
19 | correct board type as insmod argument, "insmod bttv card=2" for | |
20 | example. The file CARDLIST has a list of valid arguments for card. | |
21 | If your card isn't listed there, you might check the source code for | |
22 | new entries which are not listed yet. If there isn't one for your | |
23 | card, you can check if one of the existing entries does work for you | |
24 | (just trial and error...). | |
25 | ||
26 | Some boards have an extra processor for sound to do stereo decoding | |
27 | and other nice features. The msp34xx chips are used by Hauppauge for | |
28 | example. If your board has one, you might have to load a helper | |
29 | module like msp3400.o to make sound work. If there isn't one for the | |
30 | chip used on your board: Bad luck. Start writing a new one. Well, | |
31 | you might want to check the video4linux mailing list archive first... | |
32 | ||
33 | Of course you need a correctly installed soundcard unless you have the | |
34 | speakers connected directly to the grabber board. Hint: check the | |
35 | mixer settings too. ALSA for example has everything muted by default. | |
36 | ||
37 | ||
38 | How sound works in detail | |
39 | ========================= | |
40 | ||
41 | Still doesn't work? Looks like some driver hacking is required. | |
42 | Below is a do-it-yourself description for you. | |
43 | ||
44 | The bt8xx chips have 32 general purpose pins, and registers to control | |
45 | these pins. One register is the output enable register | |
46 | (BT848_GPIO_OUT_EN), it says which pins are actively driven by the | |
47 | bt848 chip. Another one is the data register (BT848_GPIO_DATA), where | |
48 | you can get/set the status if these pins. They can be used for input | |
49 | and output. | |
50 | ||
51 | Most grabber board vendors use these pins to control an external chip | |
52 | which does the sound routing. But every board is a little different. | |
53 | These pins are also used by some companies to drive remote control | |
54 | receiver chips. Some boards use the i2c bus instead of the gpio pins | |
55 | to connect the mux chip. | |
56 | ||
57 | As mentioned above, there is a array which holds the required | |
58 | informations for each known board. You basically have to create a new | |
59 | line for your board. The important fields are these two: | |
60 | ||
61 | struct tvcard | |
62 | { | |
63 | [ ... ] | |
4ac97914 MCC |
64 | u32 gpiomask; |
65 | u32 audiomux[6]; /* Tuner, Radio, external, internal, mute, stereo */ | |
1da177e4 LT |
66 | }; |
67 | ||
68 | gpiomask specifies which pins are used to control the audio mux chip. | |
69 | The corresponding bits in the output enable register | |
70 | (BT848_GPIO_OUT_EN) will be set as these pins must be driven by the | |
71 | bt848 chip. | |
72 | ||
73 | The audiomux[] array holds the data values for the different inputs | |
74 | (i.e. which pins must be high/low for tuner/mute/...). This will be | |
75 | written to the data register (BT848_GPIO_DATA) to switch the audio | |
76 | mux. | |
77 | ||
78 | ||
79 | What you have to do is figure out the correct values for gpiomask and | |
80 | the audiomux array. If you have Windows and the drivers four your | |
81 | card installed, you might to check out if you can read these registers | |
82 | values used by the windows driver. A tool to do this is available | |
83 | from ftp://telepresence.dmem.strath.ac.uk/pub/bt848/winutil, but it | |
84 | does'nt work with bt878 boards according to some reports I received. | |
85 | Another one with bt878 suport is available from | |
86 | http://btwincap.sourceforge.net/Files/btspy2.00.zip | |
87 | ||
88 | You might also dig around in the *.ini files of the Windows applications. | |
89 | You can have a look at the board to see which of the gpio pins are | |
90 | connected at all and then start trial-and-error ... | |
91 | ||
92 | ||
93 | Starting with release 0.7.41 bttv has a number of insmod options to | |
94 | make the gpio debugging easier: | |
95 | ||
96 | bttv_gpio=0/1 enable/disable gpio debug messages | |
97 | gpiomask=n set the gpiomask value | |
98 | audiomux=i,j,... set the values of the audiomux array | |
99 | audioall=a set the values of the audiomux array (one | |
100 | value for all array elements, useful to check | |
101 | out which effect the particular value has). | |
102 | ||
103 | The messages printed with bttv_gpio=1 look like this: | |
104 | ||
105 | bttv0: gpio: en=00000027, out=00000024 in=00ffffd8 [audio: off] | |
106 | ||
107 | en = output _en_able register (BT848_GPIO_OUT_EN) | |
108 | out = _out_put bits of the data register (BT848_GPIO_DATA), | |
109 | i.e. BT848_GPIO_DATA & BT848_GPIO_OUT_EN | |
110 | in = _in_put bits of the data register, | |
111 | i.e. BT848_GPIO_DATA & ~BT848_GPIO_OUT_EN | |
112 | ||
113 | ||
114 | ||
115 | Other elements of the tvcards array | |
116 | =================================== | |
117 | ||
118 | If you are trying to make a new card work you might find it useful to | |
119 | know what the other elements in the tvcards array are good for: | |
120 | ||
121 | video_inputs - # of video inputs the card has | |
122 | audio_inputs - historical cruft, not used any more. | |
123 | tuner - which input is the tuner | |
124 | svhs - which input is svhs (all others are labeled composite) | |
125 | muxsel - video mux, input->registervalue mapping | |
126 | pll - same as pll= insmod option | |
127 | tuner_type - same as tuner= insmod option | |
128 | *_modulename - hint whenever some card needs this or that audio | |
4ac97914 | 129 | module loaded to work properly. |
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130 | has_radio - whenever this TV card has a radio tuner. |
131 | no_msp34xx - "1" disables loading of msp3400.o module | |
994914ea MK |
132 | no_tda9875 - "1" disables loading of tda9875.o module |
133 | needs_tvaudio - set to "1" to load tvaudio.o module | |
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134 | |
135 | If some config item is specified both from the tvcards array and as | |
136 | insmod option, the insmod option takes precedence. | |
137 | ||
138 | ||
139 | ||
140 | Good luck, | |
141 | ||
142 | Gerd | |
143 | ||
144 | ||
145 | PS: If you have a new working entry, mail it to me. | |
146 | ||
994914ea | 147 | -- |
1da177e4 | 148 | Gerd Knorr <kraxel@bytesex.org> |